Arc interruption chambers for electric switching devices such as electric contactors have been known heretofore. To increase the interrupting capability of switches and contactors above levels of current and voltage that can be handled by simple contact gaps, such devices are equipped with special arc chambers which enhance arc extinction. Commonly, particularly in A.C. contactors and switches, the break-arcs are deflected into arc chutes which are provided with one or more metallic, so-called splitter-plates. These plates that are usually made of mild steel are usually flat and insulated from one another such as, for example, the plates or baffles shown in M. Muller, Pat. No. 4,080,520, dated Mar. 21, 1978, and F. P. Pardini et al patent no. 4,375,021, dated Feb. 22, 1983. Frequently, especially in contactors, these plates are somewhat remote from the contact gap or gaps as shown in the aforementioned patents. Alternatively, flat plates (not shown) which virtually embrace the contact gaps have been used in prior devices.
Magnetic forces, usually induced by the flow of the current to be interrupted, cause the break-arcs to impinge upon and penetrate the splitter-plate array in the arc interruption chamber. A buildup of pressure in front of the arc would tend to inhibit penetration of the splitter system; therefore, the splitter system is preferably more or less open (vented) at the edges opposite the arc entry edges of the plates.
Theoretically, splitter-plate systems promote current interruption by aggressive cooling of arcs and subdivision of arcs into a series of sub-arcs, partial arcs or arclets. Thus, for reliable interruption of an alternating current arc, the splitter array should (1) allow and preferably promote rapid penetration of the splitter system by the arc, and (2) not promote or allow ejection of arcs either backward toward the contact gap or forward toward the vent region. Flat splitter-plates, with straight edges or with serrated or notched edges, generally have shortcomings in either or both of the functions mentioned above. Most prior designs are troubled by unstable retention of the arcs, an effect which can be ascribed to magnetic field forces produced by currents in the plates. This action, which will hereinafter be more specifically described in connection with FIG. 1, whereby current loops are formed by irregular displacement of sub-arcs, produces forces which tend to eject the sub-arcs.
V-shaped splitter-plate structures have also been known. While these V-shaped splitter-plates inhibit ejection of sub-arcs in one direction, this V-shaped structure, however, promotes rapid ejection of sub-arcs into the vent space. This shortcoming permits a reuniting of the sub-arcs in the vent space, thus forming a single arc, or a lesser number of sub-arcs, with substantially reduced interrupting capability. Furthermore, whether the vent space is provided or not, the arcs are forceably pressed to insulation surfaces of the arc extinguishing chamber, thus aggravating thermal deterioration of the chamber.
It has, therefore been found desirable to provide improved arc extinguishing chamber structures including improved splitter-plate configurations and related splitter-plate arrays that overcome the aforementioned disadvantages and shortcomings.